Composition for casting cellulose acetate sheeting



Patented July 14, 1942 COMPOSITION FOR CASTING CELLULOSE ACETATE SHEETING Cyril J. Stand and Gustave B. Bachman, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application September 27, 1938, Serial No. 231,916

4 Claims. (Cl. 106-169) This invention relates to the casting of sheeting from cellulose esters prepared from wood pulp cellulose. v

The casting of sheeting, such as photographic film base, wrapping tissues, etc., from cellulose 'esters, is well known. A solution of cellulose ester and plasticizer, in a volatile solvent or solvent mixture, is spread in a thin, uniform layer on a highly polished surface, and the solvent allowed to evaporate. In the most common form of casting, the cellulose ester solution or dope is spread on a nickel or chromium-plated surface which forms the periphery of a rotating wheel,so that the casting process is continuous. The wheel is of large diameter, so that by the time the wheel has made approximately threefourths of a rotation after the spreading of the dope on its surface, the solvent has evaporated to a sufficient extent to set the resulting film and permit of stripping it from the casting surface. Under proper conditions, a him of cellulose ester prepared from cotton linters strips easily and uniformly from the surface. However, when attempts have been made to cast sheeting from wood pulp cellulose esters, it has been found that great difiiculty is encountered in stripping the sheeting from the casting surface. In many cases it has been impossible to strip the film from the casting surface without tearing it, thus making the film useless.

We have discovered that sheeting cast from solutions of wood pulp cellulose esters may be easily and smoothly stripped from the casting surface if there is added to the solution of wood pulp cellulose ester and plasticizer, in a volatile solvent or solvent mixture, such, for instance, as

, acetone, acetone-methanol, methylene, chloridemethanol, or ethylene chloride-methanol, a small amount of an alkyl-substituted aromatic sulfonic acid. The alkyl-substituted aromatic sulfonic acid may be used either in its free form, or in the form of its alkali metal salt, e. g. its sodium salt. The aromatic nucleus may contain, as a further substituent, a hydroxyl group or an ether group. Thus, the compounds which we have found useful for this purpose, which we may call antiherents have the structural formula where Ar is an aromatic hydrocarbon nucleus,

carbon radical, n is 1, 2, 3, or 4, and the total number of carbon atoms in the unit is at least 11. When n is 2, 3 or 4, the aliphatic hydrocarbon radicals represented by R may be the same or different. The total number of carbon atoms in the unit is preferably about 18 to 24.

The antiherent must of course be so chosen as to be soluble in the particular solvent or solvent mixture selected for preparing the cellulose ester dope. This is easily determined by experiment. In the claims, we shall refer to volatile solvents and solvent mixtures as volatile solvents. We may add from 0.1% to 5.0%, approximately, or in some cases slightly more, of the antiherent, calculated on the weight of the dope. We have found 1.0% to be a very satisfactory proportion.

As examples of our antiherents in which R" is hydrogen, we may mention tri-isopropyl naphthalene sulfonic acid, di-amyl naphthalene sulfonic acid, mono-amyl naphthalene sulfonic acid, p-hexyl biphenyl sulphonic acid,-amy1 biphenyl sulfonic acid, lauryl benzene sulfonic acid, hexadecyl benzene sulfonic acid, keryl naphthalene sulfonic acid (keryl representing the mixture of hydrocarbon radicals derived from kerosene) lauryl biphenyl sulfonic acid, octyl naphthalene sulfonic acid, tetradecyl benzene sulfonic acid, tetraisobutylene benzene sulfonic acid, tetraisobutylene naphthalene sulfonic acid, triamyl benzene sulfonic acid, tridecyl benzene sulfonic acid, and triisobutylene benzene sulfonic acid. These sulfonic acids, and the others herein mentioned, may be used either in their free form or in the form of their sodium salts, the salts being preferred as being non-corrosive to metals.

As examples of our antiherents in which R" is OH, We may mention o-amyl phenol sulfonic acid, p-tertiary-amyl phenol sulfonic acid, cetyl phenol sulfonic acid, lauryl alpha-naphthol sulfonic acid, lauryl beta-naphthol sulfonic acid, lauryl phenol sulfonic acid, lauryl pyrogallol sulfonic acid, lauryl resorcinol sulfonic acid, octadecyl 2-hydroxyl biphenyl sulfonic acid, d-octadecyl 3:5-dimethyl phenol sulfonic acid, 0cta decyl naphthol sulfonic acid, and octadecyl phenol sulfonic acid.

Among our antiherents in which R" is OR' (an ether group), we may mention, by way. of example, amyl diphenyl ether sulfonic acid.

Mixtures of any of these anti-herents, in any desired proportions, may, of course, be used.

Among the wood-pulp cellulose esters with which our novel antiherents give valuable results are cellulose nitrate, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose. acetatepropionate, cellulose acetate-butyrate, and the like. The wood-pulp cellulose organic acid esters may be used in the hydrolyzed or unhydrolyzed condition. If water or methanol is present in the dope, the amount of antiherent required is greater than when neither of these compounds is present, and increases with increasing amounts where Ar is an aromatic hydrocarbon nucleus, R is an aliphatic hydrocarbon radical, X is an atom selected from the group consisting of hydrogen atoms and alkali metal atoms, R" is selected from the group consisting of hydrogen, OH, and OR', R' being selected from the group consisting of aliphatic and aromatic hydrocarbon radicals, n is an integer between, 1 and 4, inclusive, and the unit contains at least 11 carbon atoms.

2. A solution, in a volatile solvent, of wood pulp cellulose ester and plasticizer, adapted to be cast on a casting surface to form transparent sheeting which can be readily stripped from the casting surface, containing, as a substance for facilitating stripping of the sheeting from the casting surface, from 0.1% to 5% of a compound soluble in the volatile solvent, having the structural formula H-Ar-SOz-OX where Ar is an aromatic hydrocarbon nucleus, R. is an aliphatic hydrocarbon radical, X is an atom selected from the group consisting of hydrogen atoms and alkali metal atoms, 1:. is an integer between 1 and 4, inclusive, and the unit containsat least 11 carbon atoms.

3. A solution, in a volatile solvent, of wood pulp cellulose ester and plasticizer, adapted to be cast on a casting surface to form transparent sheeting which can be readily stripped from the casting surface, containing, as a substance for facilitating stripping of the sheeting from the casting surface, from 0.1% to 5% of a compound soluble in the volatile solvent, having the structural formula HO-Ar-SOrOX where Ar is an aromatic hydrocarbon nucleus, R is an aliphatic hydrocarbon radical, X is an atom selected from the group consisting of hydrogen atoms and alkali metal atoms, 11. is an integer between 1 and 4, inclusive, and the unit contains at least 11 carbon atoms.

4. A solution, in a volatile solvent, of wood pulp cellulose ester and plasticizer, adapted to be cast on a casting surface to form transparent sheeting which can be readily stripped from the casting surface, containing, as a substance for facilitating stripping of the sheeting from the casting surface, from 0.1% to 5% of a compound' soluble in the volatile solvent, having the structural formula R"OArSOz-OX where Ar is an aromatic hydrocarbon nucleus, R is an aliphatic hydrocarbon radical, X is an atom selected from the group consisting of hydrogen atoms and alkali metal atoms, R' is selected from the group consisting of aliphatic and aromatic hydrocarbon radicals, n is an integer between 1 and 4, inclusive, and the unit -(R)- contains at least 11 carbon atoms.

CYRIL J. STAUD. GUSTAVE B. BACHMAN. 

